1.

\(a,\left(-xy\right)\left(-2x^2y+3xy-7x\right)\)

\(=2x^3y^2-3x^2y^2+7x^2y\)

\(b,\left(\dfrac{1}{6}x^2y^2\right)\left(-0,3x^2y-0,4xy+1\right)\)

\(=-\dfrac{1}{20}x^4y^3-\dfrac{1}{15}x^3y^3+\dfrac{1}{6}x^2y^2\)

\(c,\left(x+y\right)\left(x^2+2xy+y^2\right)\)

\(=\left(x+y\right)^3\)

\(=x^3+3x^2y+3xy^2+y^3\)

\(d,\left(x-y\right)\left(x^2-2xy+y^2\right)\)

\(=\left(x-y\right)^3\)

\(=x^3-3x^2y+3xy^2-y^3\)

2.

\(a,\left(x-y\right)\left(x^2+xy+y^2\right)\)

\(=x^3-y^3\)

\(b,\left(x+y\right)\left(x^2-xy+y^2\right)\)

\(=x^3+y^3\)

\(c,\left(4x-1\right)\left(6y+1\right)-3x\left(8y+\dfrac{4}{3}\right)\)

\(=24xy+4x-6y-1-24xy-4x\)

\(=\left(24xy-24xy\right)+\left(4x-4x\right)-6y-1\)

\(=-6y-1\)

#Toru

a: \(\dfrac{x^2+2xy+y^2}{x+y}=x+y\)

b: \(\dfrac{64x^3+1}{4x+1}=16x^2-4x+1\)

a) \(\left(x^2+2xy+y^2\right):\left(x+y\right)=\left(x+y\right)^2:\left(x+y\right)=x+y\)

b) \(=\left[\left(5x+1\right)\left(25x^2-5x+1\right)\right]:\left(5x+1\right)=25x^2-5x+1\)

c) \(=\left(y-x\right)^2:\left(y-x\right)=y-x\)

\(a,=\left(x+y\right)^2:\left(x+y\right)=x+y\\ b,=\left(5x+1\right)\left(25x^2-5x+1\right):\left(5x+1\right)=25x^2-5x+1\\ c,=\left(y-x\right)^2:\left(y-x\right)=y-x\)

Đáp án cần chọn là: A

b: (x-y)(x^2-2x+y)

\(=x^3-2x^2+xy-x^2y+2xy-y^2\)

\(=x^3-2x^2-x^2y+3xy-y^2\)

c: \(\left(x^2-y\right)\left(x+y^2\right)-\left(x-y\right)\left(x^2+xy+y^2\right)\)

\(=x^3+x^2y^2-xy-y^3-\left(x^3-y^3\right)\)

\(=x^2y^2-xy\)

d: \(3x\left(2xy-z\right)-5y\left(x^2-2\right)+3xz\)

\(=6x^2y-3xz-5x^2y+10y+3xz\)

\(=x^2y+10y\)

Đây nè bạn.

a) Ta có: \(M=x^2-2xy+y^2-10x+10y\)

\(=\left(x-y\right)^2-10\left(x-y\right)\)

\(=9^2-10\cdot9=-9\)

Lời giải:

a) (x2 + 2xy + y2) : (x + y)

= (x + y)2 : (x + y)

= x + y

b) (125x3 + 1) : (5x + 1)

= [(5x)3 + 1] : (5x + 1)

= (5x + 1)[(5x)2 – 5x + 1]] : (5x + 1)

= (5x)2 – 5x + 1

= 25x2 – 5x + 1

c) (x2 – 2xy + y2) : (y – x)

= (x – y)2 : [-(x – y)]

= -(x – y)

= y – x

Hoặc (x2 – 2xy + y2) : (y – x)

= (y2 – 2yx + x2) : (y – x)

= (y – x)2 : (y – x)

= y – x

\(\text{a) (x^2 + 2xy + y^2) : (x + y)}\\ \left(x+y\right)^2:\left(x+y\right)=x+y\)

a)x+y

b)25x²-5x+1

c)-x+y

Theo bài ra, ta có: \(x^2-y=y^2-x\Leftrightarrow x^2-y^2=-x+y\)

\(\Leftrightarrow\left(x-y\right)\left(x+y\right)=-\left(x-y\right)\)

\(\Leftrightarrow\left(x+y\right)=-1\)

Ta lại có: \(A=x^2+2xy+y^2-3x-3y=\left(x+y\right)^2-3\left(x+y\right)\)

Thay x+y=-1 vào biểu thức A, ta được: \(A=\left(-1\right)^2-3.\left(-1\right)=1+3=4\)

Vậy A=4